Magnetic structure



1'06. COMPOSITIONS,

COATiNG R PLAS 'C atented Mar. 10, 1931 UNITED STATES PATENT OFFICE JACK CHAMBERS CEASTON AND JOHN PERCY JOHNS, OF ALDWYCH, LONDON, ENGLAND; ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0] NEW YORK MAGNETIC STRUCTURE 80 Drawing. Application fled September 81, 1889, Serial No. 894,381, and in Great Britain October 4,

This invention relates to the manufacture particles of the heat treated core. A considof ma etic structures such as cores for loaderation of the action of pressing shows that ing 0011s and the like, of the type in which during this operation the particles are per finely divided magnetic particles, mixed with manently deformed and moulded so as to fit 5 an insulating material, are compressed into a closely together and interlock. Unless persuitable form. manent deformation takes place the particles In this manufacture it is necessa to use will not be able to fit together sufliciently considerable pressure in order to o tain a closely to give the desired values of permeacore of high permeability, and if the magnetic bility to the finished cores. The use of lower material is of such character that its permepressures would produce less strain, but the ability is sensitive to strain, very many probarticles would not be keyed to ether satislems arise as to the treatment, components actorily, spaces would remain etween the and conditions for roducing a most satisfacparticles, and the permeability would below. tory structure. This is most noticeable where it seemed that if the particles could be caused the magnetic material is a nickel iron alloy to move slightly apart after the compression a high degree of compression must be reached,

for although this alloy is capable of aving and then given more freedom to move, the developed in it an extremely high-permeasetting up of strains wouldbe reduced. Thus bility this permeability is very considerabl by causing the insulation to perform this reduced by mechanical strain. Thus, thoug function, an improved core was roduced.

The invention may be carrie out in the the ma etic particles in the finished core following manner should uring and after the subseiprient heat A ma netic dust is preppred from an alloy treatment he as far as possible ee from contammga on 0% nic el and the remainstrain. der iron. It is desirable to anneal the ar- An object of the resent invention is to ticles at this stage. The annealed partlcles change a physical c aracteristic of the inare then mixed with chromicacid, sodiu sulatmg material between the compression silicate and talc in the same manner and pro stgge and the subsequent heat treatment.

his may be effected by subjecting the core W. Andrews et al., No. 1,669,643, issued May after compression and prior to the final an- 15, 1928. The mixture is then compressed fluid is one which being partly absorbed b nealing treatment, to a fluid, for a length of into core form preferably with a pressure of time sufiicient for the desired physical charapproximatel 200,000 pounds persquareinch acteristics to be obtained. as m the method disclosed in the aforemen- In thepreferred form of the invention the tioned patent. The core is allowed to hang freely in an atmosphere of definite humidity th e insulation causes it to swe and uring for a iven length of time. The degree of W115 as described in the U. S. patent to J a sub'seliiienfhattreatmentis liberated, at humidity of the air in the conditionin chamv mleast partially. If the insulatin material ber, the temperature of the air, and t e time 3 d soillum sihcomprises chromic acid an /or of conditioning may be varied over wide gatepr such ot er ygroscopic subliance, the limits. In general, the effect of conditionq, fluidmay be water water va our 9r a humid in becomes more marked as the humidity is case it may be desirable rai sed, but there seems to be little advantage 45 the invention have been found to give very to dry the core immediately prior to theanin employing a higher humidity than that of nealing treatment. Cores made according to saturated air at room temperature- Good results have been obtained by condilow hysteresis losses and the invention also tioning the corerings for 18 hours in a closed enables a greater control to be exercised over vessel in which the air is maintained satuthe permeabilit of the finished core. rated with water vapor at room temperature.

It is believe that the improvements are After this treatment the cores are preferably due to the reduction of strain in the magnetic subjected to a final annealing heat treatment to specific similar to that disclosed in the aforementioned patent, after which they are ready for service. Measurements made on a typical batch of core rings conditioned in this manner showed them to have a core loss of 68.4 ohms per henry. when tested at a frequency of 3000 cycles per second. Similar cores having the same germeability, but which were not conditio'ne loss of 89.1 ohms per henry when tested under similar conditions. I The operation of conditioning thus resulted in a reduction of the core loss amountingnt:t 23.3%.

ead of conditioning in moist air, the cores may be Elaced in water, thus going to the limit of umidity. The efl'ect to this treatment as regards improvements in magnetic properties is substantially the same as if the rings were 'kept in saturated air at room temperature, but there is a tendency for the mechanical strength of the cores to be impaired when the cores are immersed in water and, therefore, the treatment with humid air is referable. If the water treatment is use care must be taken to limit the time of exposure to the water or the cores may fall to pieces.

Althoughthe invention has been described by way 0 exam le with particular reference insulating and conditioning mediums, it will be clear that other insulatin materials and conditioning fluids may be use and in fact that any insulating material ma be used, the physical characteristics of whi may be changed by conditioning in any suitable fluid between the compression stage and the subsequent heat treatment.

Also, though the invention has been described with particular reference to the manufacture of cores, it will be clear that it may be employed in the manufacture of structures of any other form which are made by compressin insulated finely divided magnetic parti es.

What is claimed is:

1. A method of producing a ma etic structure or core which comprises insufa lzing particles of magnetic material compressing the insulated particles to a suita le form, subecting the insulated,,compressed particles 'to a fluid substance for a suflicient length of time to ap reciably change the physical charteristics o the insulating material, and heat treating the resulting product.

2. A method of producing a magnetic structure comprising magnetic particles insulated from each other, wherein the core after bein compressed, and previous to an annealm eat treatment, is subjected to a fluid unt1l the physical properties of the insulating material are a cagreciably modified whereby the magnetic aracteristics Eli?- ducedinthe final eat treatment maybe y developed.

were found to have a core.

3. A method of producing a magnetic structure which comprises insulating magnetic particles, compressing the insulated articles into a homo eous bod subjecting said body to a flui for a suflicient length of time to cause the insulation therein to swell appreciably, and heat treating the resulting product.

4. The method of claim 1 in which said compressed insulated particles are subjected to' said fluid for a time suflicient to enable an a preciable portion of said fluid to be absor d b the insulation, at least a portion of which uid is liberated during the subsequent annealing heat treatment.

5. The method of claim 1 and in which said insulating material comprises a hcygrd scopic substance, and said fluid in udes water.

6. The method of claim 1 and in which said magnetic particles are insulated with an insulating material including chromic ac1d and sodium silicate.

7. The method of claim 1 and in which said magnetic material comprises an alloy mcluding nickel and iron.

8. The method of claim 1 and m which said fluid substance is in vapor form.

9. The method of claim 1 in which the fluid substance to which the insulated compressed articles are subjected comprises air satura with water vapor.

In witness whereof, we hereunto subscribe our names this twentieth day of August, 1929.

JACK CHAMBERS GHASTON. JOEI PERCY JOHNS. 

